Most digital communication systems require synchronization between near-end and far-end link partners to operate properly. A common method to obtain clock synchronization in a receiver is to extract the far-end clock from the received signal. One timing recovery method used in many communications devices is based on the well-known Mueller and Müller (MM) algorithm, and obtains a recovered clock based on one of two timing functions, in which it is assumed that the channel between the link partners is linear.
While this assumption is reasonable for many communications systems, since both a modulator of a transmitter and a physical medium that couples the partners may be considered linear, there are some communication systems where this linearity condition is not fulfilled. One example is the case of systems that employ Tomlinson-Harashima-Precoding (THP), which is a method for combating inter-symbol interference (ISI) in the transmitter side, with no significant peak-to-average ratio enlargement. This method was adopted by the Institute of Electrical and Electronics Engineers (IEEE) for its so-called 10GBASE-T, i.e., Draft Amendment P802.3an/Draft 3.1, 2005 standard, and is also used in many other communication systems and standards, e.g., asynchronous digital subscriber line (ADSL). Thus in many systems, clock recovery based on a MM algorithm is not possible.